The present disclosure relates to a transmission device that includes a first clutch and a second clutch that is disposed around the first clutch.
A transmission device of such a type has heretofore been known, which includes a clutch C1 structured as a multi-plate friction hydraulic clutch, and also includes a clutch C2 that is structured as a multi-plate friction hydraulic clutch and is disposed inside the clutch C1 (refer to Japanese Patent Application Publication No. 2012-215283, for example). The clutch C1 of the transmission device includes a clutch drum that includes a first outer cylinder portion, a first sidewall portion extending inward in the radial direction from the first outer cylinder portion, and an inner cylinder portion extending in the axial direction from the inner circumferential portion of the first sidewall portion; a clutch piston that defines a first engagement-side oil chamber with the clutch drum; and a cancel plate that defines, with the clutch piston, a first cancel oil chamber for canceling centrifugal hydraulic pressure produced in the first engagement-side oil chamber. A clutch drum of the clutch C2 disposed inside the clutch C1 includes a second outer cylinder portion and a second sidewall portion that extends inward in the radial direction from the second outer cylinder portion. The clutch drum of the clutch C2 is fastened together with the cancel plate of the clutch C1 to the first sidewall portion of the clutch drum of the clutch C1 via rivets.